Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 6 2004 10.5194/acpd-4-7403-2004 http://www.atmos-chem-phys-discuss.net/4/7403/2004/ http://www.atmos-chem-phys-discuss.net/4/7403/2004/acpd-4-7403-2004.html http://www.atmos-chem-phys-discuss.net/4/7403/2004/acpd-4-7403-2004.pdf 7403 7431 2004-11-09 Column ozone and aerosol optical properties retrieved from direct solar irradiance measurements during SOLVE II W. H. Swartz J.-H. Yee R. E. Shetter S. R. Hall B. L. Lefer J. M. Livingston P. B. Russell E. V. Browell M. A. Avery The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA National Center for Atmospheric Research, Boulder, Colorado, USA SRI International, Menlo Park, California, USA NASA Ames Research Center, Moffett Field, California, USA NASA Langley Research Center, Hampton, Virginia, USA now at: University of Houston, Department of Geosciences, Houston, Texas, USA Direct observation of the Sun at large solar zenith angles during the second SAGE&nbsp;III Ozone Loss and Validation Experiment (SOLVE&nbsp;II)/Validation of International Satellites and study of Ozone Loss (VINTERSOL) campaign by several instruments provided a rich dataset for the retrieval and analysis of line-of-sight column composition, intercomparison, and measurement validation. A flexible, multi-species spectral fitting technique is presented and applied to spectral solar irradiance measurements made by the NCAR Direct beam Irradiance Atmospheric Spectrometer (DIAS) on-board the NASA DC-8. The approach allows for the independent retrieval of O<sub>3</sub>, O<sub>2</sub>&middot;O<sub>2</sub>, and aerosol optical properties, by constraining Rayleigh extinction. We examine the 19 January 2003 and 6 February 2003 flights and find very good agreement of O<sub>3</sub> and O<sub>2</sub>&middot;O<sub>2</sub> retrievals with forward-modeling calculations, even at large solar zenith angles, where refraction is important. Intercomparisons of retrieved ozone and aerosol optical thickness with results from the Ames Airborne Tracking Sunphotometer (AATS-14) are summarized.